Lot Quality Assurance Sampling for Monitoring and Evaluation of Immunization Coverage in District Solan, Himachal Pradesh, India, 2011

Abstract

Introduction: Immunization is one of the most cost effective interventions amongst 32 well understood prevention and treatment interventions that target the goals of the child health. Despite of overall high immunization coverage in Solan district, there are low performing immunization pockets present due to migrant labour dominant un-uniformly distributed industry in the district (a case of polio was detected in 2007). We conducted a study to assess whether the immunization coverage in each of the five health blocks of and the entire district Solan is at or below 80% using Lot Quality Assurance Sampling (LQAS). Methods: A cross-sectional study was conducted in all the five health blocks of Solan district. The hypothesis that <80% coverage is 'unacceptable' was stipulated. The sample size, assuming binomial approximation, with 5% level of significance, required to test the null hypothesis, was computed as 36. Critical value (the number of unimmunized children) was chosen as 3. Immunization status of each child was assessed by interviewing the child's mother/guardian. If the number of unimmunized children in the sample exceeded the critical value 3, then the immunization coverage in the block was to be regarded as below 80%. Results: Out of the five lots/blocks of the district Solan, only one lot/block has achieved acceptable immunization coverage of more than 80%. Conclusion: This study demonstrated the utility of LQAS technique in identifying 'unsatisfactory' pockets at smaller area level and district health authorities were recommended to take remedial action to improve immunization coverage in these areas.